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Coverage — msgpack 3.3.0

npm run coverage runs both halves and fails the build under 95%.

Target Metric Result Gate
lib/ + bin/ (c8) statements 100% ≥ 95%
lib/ + bin/ (c8) branches 100% ≥ 95%
lib/ + bin/ (c8) functions 100% ≥ 95%
lib/ + bin/ (c8) lines 100% ≥ 95%
src/ (gcovr) lines 95.7% (1002/1047) ≥ 95%
src/ (gcovr) branches 95.5% (976/1022) ≥ 95%
src/ (gcovr) functions 100% (66/66) —

deps/ is excluded from the native report; the vendored msgpack-c is not our code. build/ is rebuilt without instrumentation at the end of coverage:native, including when the gate fails, so the working tree is never left with a --coverage addon. npm install and node-gyp rebuild are unaffected: coverage flags only apply when msgpack_coverage=1 is passed.

Measured on Linux / Node 20 / GCC. Reproduce with:

npm run coverage          # both, with thresholds
npm run coverage:js       # c8 only
npm run coverage:native   # gcovr only

Remaining uncovered JS

None. lib/msgpack.js, bin/json2msgpack and bin/msgpack2json are at 100% on all four metrics.

One bin/json2msgpack path deserves a note because it looked unreachable at first: the msgpack.pack() failure arm. JSON.parse cannot produce a function, a circular structure, a Symbol or a BigInt, so almost every pack error is out of reach from real JSON. It can produce arbitrarily deep nesting, which trips the 512-level pack cap — that is what test/cli.test.js uses to cover the arm.

Remaining uncovered native lines (20 of 493)

Every one is an error arm that cannot be entered from JS without stubbing malloc or V8. None were removed to raise the number.

Lines Code Why it is not reached
307–308 default: return kScanParse; in ScanOne Dead by construction. The switch runs only for bytes 0xc0–0xdf (everything else is handled by the fixint/fixmap/fixarray/fixstr tests above it) and all 32 of those values have explicit cases.
370, 390 Error("Error serializing object") in CallNoArgs / ThrowCaught Fallback for an empty MaybeLocal with no pending exception. V8 always sets an exception before returning an empty Maybe.
433–434 Unmark(arr); throw after msgpack_pack_array msgpack_sbuffer_write fails only when realloc fails.
486–487 Unmark(obj); throw after msgpack_pack_map Same.
567 if (rc) throw in JsToMsgpack Same — every rc comes from an sbuffer write.
624 throw Error("cannot unpack map key") Needs Nan::To<v8::String> to fail. Decoded map keys are nil / bool / number / string / Buffer / Array / plain Object, none of which can throw in ToString.
631, 634 default: throw Error("Encountered unknown object type") in MsgpackToJs All 11 msgpack_object_type values are handled explicitly.
675 throw Error("Error initializing packing buffer") msgpack_sbuffer_new returns NULL only out of memory.
735 throw after msgpack_pack_array in Pack Allocation failure only.
809–813, 815 MSGPACK_UNPACK_CONTINUE / parse-error tail of Unpack ScanOne walks the same grammar first with limits at or below the vendored library's own (511 vs 512 nested containers, the same 1 000 000 element cap), so once it returns kScanOk, msgpack_unpack_next can only succeed. The arms stay so a future divergence fails closed instead of reading result.data uninitialised.

Remaining uncovered native branches in msgpack.cc (2)

Line Code Why
154 switch (b) in ScanOne The default: edge — see lines 307–308 above. It cannot be excluded on its own without also dropping the 30 covered case edges on the same line, so it is left in and counted against us.
611 switch (mo->type) in MsgpackToJs Same, for the default: edge covering the complete msgpack_object_type enum.

About the native branch number

Raw gcov branch data for this file is dominated by artefacts, not by test gaps. The three numbers, all from the same run:

gcovr invocation Branches Result
--no-markers (fully raw) 636 70.6%
--no-markers --exclude-throw-branches --exclude-unreachable-branches 502 86.3%
as shipped (markers honoured) 402 99.5%

Two mechanisms account for the difference, and both are worth understanding before reading 99.5% as "almost everything is tested":

  1. --exclude-throw-branches drops 134 edges. This is a compiled-with- exceptions C++ file, so gcov emits a "call threw / call returned" edge for nearly every function call inside a try. Those are not decisions in the source and no test can flip most of them.

  2. GCOVR_EXCL_BR_* markers in src/msgpack.cc drop a further 100 edges across 45 lines. Each marker carries its reason inline. They are comments only — no production code was deleted, and every guarded branch is still compiled and still runs. The full set:

    • Allocation-failure arms (lines 432–434, 485–487, 529, 543, 553, 566, 567, 674, 675, 734, 735). msgpack_pack_array/map/str/bin/*_body fail only when the sbuffer cannot grow.
    • Skip() after a successful CheckBytes() (lines 144, 160, 168, 176, 185, 194, 203, 256, 264, 272). CheckBytes returns kScanOk only when n <= remaining, so the following Skip(&c, n) cannot fail. Ten identical dead edges.
    • CheckContainer's inner limit test (line 85). Both disjuncts are already excluded: n > kMaxContainer returned at the top of the function, and items is at most 2 * kMaxContainer (2 000 000), far below kMaxBytes (33 554 432). Kept as defence in depth in case either constant changes.
    • Empty-MaybeLocal guards (lines 351, 369, 370, 389, 390, 623, 624). V8 only returns an empty Maybe with an exception pending, and a private- symbol read (IsMarked) runs no interceptor or Proxy trap at all.
    • ThrowCaught(try_catch) call sites (lines 401, 410, 419). ThrowCaught always throws; the "returned normally" edge is dead.
    • ~PackBuffer's sb_ == NULL guard (line 686). sb_ is non-NULL from the constructor onward (a throwing constructor runs no destructor) and is cleared only on the destructor's last line.
    • MsgpackToJs unknown-type throw (line 634) and Pack's catch dispatch (line 752) and Unpack's catch dispatch (line 802) — nothing inside those scopes throws a non-MsgpackException.
    • Unpack's post-ScanOne tail (lines 796, 809, 810, 812, 815). See the line table above.

    Excluding a line removes all of its edges, including covered ones, so several of these markers cost us covered edges too (line 752, for example, gives up three covered edges to drop one dead one). The exclusions are conservative in that direction.

If you want the un-gated view at any time:

gcovr --root . --filter src/ --exclude deps/ --no-markers --txt-metric branch --txt -

What the new tests cover

  • test/bigint.test.js — #37 Number-vs-BigInt rule: uint64 of 1 stays Number, MAX_SAFE_INTEGER stays Number, reporter uint64 round-trips as BigInt, in-range BigInt still uses integer wire (not ext), out-of-range BigInt packs as ext 0x42 (uint256, 64-bit boundaries, nested, 256-byte cap), rounded Number bits are not recovered.
  • test/coverage-native.test.js (57 tests) — hand-built wire buffers for every MessagePack format family, including the ones pack() never emits (float32, str8/16/32, bin16/32, array32, map16/32, all eight ext forms, negative fixint); a truncation point for every header and payload; kMaxBytes / kMaxContainer / kMaxDepth rejections; 0xc1; the pack-side type dispatch (Symbol, non-finite numbers, integer edges, undefined, zero-argument and multi-argument pack); Date failure modes; toJSON failure modes and mark cleanup; and a worker that nests 600 packs deep to saturate the thread-local sbuffer pool and reach the "pool is full, free it" arm of ~PackBuffer.
  • test/pack-hints.test.js — pack(value, { type, family, interpret }) wire types, last-arg options detection (host objects, Proxies, ownKeys throws), and the reachable miss paths in src/pack_hints.inc. Unreachable arms (empty info[1], kTypeNone / kFamilyNone defaults, hinted kMaxPackDepth) are marked GCOVR_EXCL_*, not deleted. Native overall stays above the 95% gate (pack_hints.inc itself is 91% branches because switch default: edges sit on the same line as covered cases).
  • test/lazy.test.js — #40 unpack(buf, { lazy: true }): one-arg eager identity, nested o.c[1] without reading siblings, __proto__ / constructor as own properties, oversized headers still throw, incomplete buffers still return null, toJSON / JSON.stringify / util.inspect match eager unpack, nested BigInt, non-object second args, toJSON this checks, and str/bin reads after the caller Buffer is transferred. Lazy OOM / empty-Maybe / ObjectTemplate-failure / CopyBuffer-failure arms are marked GCOVR_EXCL_*, not deleted.
  • test/cli.test.js (12 tests) — the exit-1 paths of both CLIs: invalid JSON, empty stdin, a pack rejection reachable from real JSON, an unparseable byte, an oversized header, incomplete input both alone and after a good frame, and chunked stdin.